WO2008054245A1

WO2008054245A1 - Pressure sensor

Info

Publication number: WO2008054245A1
Application number: PCT/RU2007/000544
Authority: WO
Inventors: Vasily Radionovich Rassomagin
Original assignee: Vasily Radionovich Rassomagin
Priority date: 2006-11-02
Filing date: 2007-10-08
Publication date: 2008-05-08
Also published as: EP2088412A1; RU2006140031A

Abstract

The inventive pressure sensor comprises a membrane (1) provided with an inductive element, which is embodied in the form of a flat conductive winding of an inductance coil (2) placed on the internal surface (3) of the membrane coaxially to it, and a measuring-and-recording unit (4). The sensor also comprises a lid which is made of a dielectric material in the form of a disc (5) and is provided with flat conductive s windings of a power pumping coil (7) and of the information read out coil (8) of the measuring-and-recording unit and a conductive coating, which are arranged on the internal surface thereof, wherein said lid (5) is placed on themembrane (1) made of a dielectric material, preferably in the form of a fused quartz. Said sensor can be widely used in the devices for automatic pressure measurement.

Description

PRESSURE METER

FIELD OF THE INVENTION The invention relates to automation and computer engineering, and is intended for use in pressure measurement automation devices.

State of the art

A known pressure sensor (see RF patent N <> 1699244, IPC G01L9 / 10.opybl. 27.02.1995), which contains a hollow cylindrical body and a measuring unit with an inductor. The housing is installed in the wall of the measurement object. The housing is a short-circuited coil for the remote coil of the measuring unit. The housing can be mounted with an external surface facing either inward of the volume where the pressure is measured, or outside the volume under investigation. In the latter case, the coil can be installed outside the housing, while the pressure is supplied to the internal cavity of the housing. If the housing is used as a compensation sensing element along with the working housing, the coil of the measuring unit is located inside the cavity formed by the housings and can be made of two halves inductively coupled to a common excitation coil.

The cases can be made of a strain gauge material, for example manganin. The sensor operates as follows.

Under the influence of the measured pressure in the cylindrical casing, mechanical stress arises, causing a change in the electrical resistance of the closed loop formed by the casing wall. Housing Compression Pressure

SUBSTITUTE SHEET (RULE 26) at the same time to reduce the resistivity of the strain gauge material of which the housing is made, to reduce the diameter and increase the thickness of the wall of the housing. All these factors act in accordance with the direction of decreasing the equivalent resistance of the short-circuited coil formed by the cylindrical wall of the housing and in electromagnetic communication with the coil of the measuring unit. Thus, the measured pressure is converted into a change in the total (complex) resistance of the coil, which is then recorded by the measuring unit.

In the specified sensor, when the pressure changes, the total (complex) resistance of the coil changes, the value of which judges the pressure value. The presence of a short-circuited coil in the design of the indicated sensor reduces the accuracy of pressure measurement, since the power released in the short-circuited coil leads to a change in its temperature and electrical resistance, and, consequently, the total (complex) resistance of the coil.

The closest analogue of the proposed pressure sensor is a device representing a pressure sensor (see RF patent JVb 2075896, IPC G 01 L 9/10, published on 03.20.1997).

The specified pressure sensor - the prototype contains a hollow cylindrical body, divided by a flexible elastic element into two chambers, one of which is in communication with the measured medium, and electromagnetic elements. The housing is made detachable with an internal annular groove located in the plane of the connector, the flexible elastic element is made in the form of a disk membrane of a dielectric gas-tight material, fixed in the said annular groove, on each side of the membrane

SUBSTITUTE SHEET (RULE 26) the introduced inductive elements are formed in the form of flat conductive spirals, and in the center of the membrane on each side there are introduced first contact pads connected to the inner turns of flat conductive spirals, a through sealed metallized hole is made in the first contact pads and in the membrane for connecting the internal turns of the spirals between by themselves, flat conductive spirals are made in relation to each other with the opposite direction of the twist of the turns of t of the center of the membrane, the external turns of flat conductive spirals are connected to two introduced contact pads located on the sides of the membrane near its edges and being the first and second terminals of the sensor, and the electromagnetic elements are made in the form of two flat inductor coils located coaxially and symmetrically in the cells of the sensor housing in relation to the membrane, while the ends of the flat inductors are respectively the third, fourth, fifth and sixth conclusions of the sensor connected to the measuring unit ku.

In the specified pressure sensor, when the pressure changes, the inductance of the flat conductive spirals formed on each side of the membrane changes, the magnitude of which determines the pressure value.

The low measurement accuracy of the prototype sensor is determined by the presence of a through metallized hole in the membrane, due to the low strength of the metallized hole with a large number of pressure cycles. The specified pressure sensor cannot measure the pressure of aggressive media due to flat conductive spirals formed on each side of the membrane.

SUBSTITUTE SHEET (RULE 26) Disclosure of invention

The objective of the invention is to develop a simple in design, more sensitive and reliable in operation, especially in aggressive environments, the pressure sensor. The problem is solved by using the features specified in the 1st paragraph of the claims common to the prototype, such as a pressure sensor containing a membrane with an inductive element made in the form of a flat conductive coil of an inductor and a measuring and registration unit, and distinctive essential features, such how the sensor is equipped with a cover of dielectric material in the form of a disk mounted on a membrane of dielectric material, an energy pumping coil, an information reading coil flax-registration unit and a conductive coating, while the width of the first and last turns of a flat conductive spiral of the inductor is greater than the width of the turns of the middle part of the inductor.

In paragraph 2 of the formula reflected the features of the basic elements of the sensor, namely the lid and membrane are preferably made of fused silica.

The peculiarity of the conductive coating of the cover is reflected in paragraph 3 of the claims, namely, the conductive coating is made in the form of a metal strip located on a circle on the inner surface of the cover above a flat electrically conductive coil of the inductor located on the inner side of the membrane.

The design feature of the energy pumping coil, the information reading coil is reflected in paragraph 4 of the claims, namely the energy pumping coil, the reading coil

SUBSTITUTE SHEET (RULE 26) information of the measuring and recording unit is made in the form of flat conductive spirals and placed on the inner surface of the lid.

In the proposed pressure sensor, when the pressure changes, the self-capacitance of the inductor changes, which is the capacity distributed along the winding of the inductor.

The proposed pressure sensor has high manufacturability, since the sensitive element is the inductance coil of the oscillatory circuit made by printing on the surface of fused silica.

High accuracy of pressure measurement is determined by the use in the design of the proposed pressure sensor fused silica. Fused silica has low temperature coefficients of expansion and dielectric constant, which determines the high temperature stability of the inductance and self-capacitance of the inductor - a sensitive element of the proposed pressure sensor. The membrane of the proposed pressure sensor, made of fused silica, has virtually no hysteresis, is chemically inert.

The above set of essential features allows you to get the following technical result - the expansion of the arsenal of technical means for measuring pressure, improving the manufacturability and accuracy of pressure measurement.

Brief Description of the Drawings

The device of the proposed pressure sensor is illustrated by the following drawings: FIG. 1 Section of the pressure transducer according to A-A FIG. 2 and FIG. 3.

SUBSTITUTE SHEET (RULE 26) FIG. 2 View of the membrane from the side of the inductor.

FIG. 3 Cover view from the inside.

In FIG. 4 shows a structural diagram of one of the possible options for the technical implementation of the proposed pressure sensor. The implementation of the invention

The pressure sensor contains (Fig. L) a membrane 1 with an inductive element made in the form of a flat conductive spiral of an inductor 2 (made of platinum) located on the inner side 3 of the membrane 1 and coaxially with respect to it and a measuring and recording unit 4 ( figure 4). The sensor is equipped with a cover of dielectric material in the form of a disk 5, on the inner surface 6 of which are placed flat conductive spirals of the windings of the energy pumping coil 7, information reading coils 8 of the measuring and recording unit 4 and the conductive coating 9. The cover 5 is mounted on a membrane 1 of dielectric material, which are preferably made of fused silica. The membrane 1 and the cover 5 are interconnected by glass junction.

The interior of the proposed pressure sensor is evacuated. If necessary, the proposed pressure sensor is shielded.

The membrane 1 of the proposed pressure sensor is made in the form of a disk with a small recess in the Central part and serves as a housing. The conductive coating 9 (Fig. H) is made in the form of a metal strip (made of platinum), located on a circle on the inner surface 6 of the cover 5 above the flat conductive spiral of the inductor 2, located on the inner side 3 of the membrane 1. The width of the first 10 and

SUBSTITUTE SHEET (RULE 26) the last 11 turns of a flat conductive spiral of the inductor 2 is larger than the width of the turns of the middle part 12 of the inductor 2 (figure 2).

As an example, the implementation of the proposed pressure sensor, a device that implements a method for measuring the movements of controlled objects (see the description of the patent of the Russian Federation Jfs 2207498, CL G 01 B 7/00. "Method of measuring the movements of controlled objects"), in which the capacitor is excluded, and the function of the acting object is performed by a conductive coating located on the inner surface of the pressure sensor cover.

The specified device contains an inductor 2 and a measuring and recording unit 4. An inductor 2 contains a first turn 10, a last turn AND (sections of the winding of the inductor 2 adjacent to the ends of the winding of the inductor 2) and the middle part 12. The inductor 2 performs the function of an oscillatory contour (figure 2).

The measuring and recording unit 4 (Fig. 4) contains an energy pumping winding 7, an information reading winding 8, the outputs of which are connected to the inputs of the measuring amplifier 13, the output of which is connected to the input of the comparator 14, the output of which is connected to the sync input of the frequency divider (in Fig. 4 not shown) of the shaper 15 time intervals, with the first input of the OR element 16 and with the trigger input of the trigger 17. The information input of the trigger 17 is connected to the output of the multivibrator (not shown in Fig. 4) of the shaper 15 time intervals, and the direct output One is connected to the start input of the meter 18 time intervals, the group of information inputs / outputs of which is connected to the computer 19 via a board (not shown in Fig. 4)

SUBSTITUTE SHEET (RULE 26) IEEE 488 CARD, installed in the computer 19, and is a common channel (CPC).

The shaper 15 time intervals through the serial communication channel RS-232C is connected to the computer 19, the second input of the OR element 16 is the input 20 to start continuous undamped oscillations of the oscillatory circuit, and the open collector output pulled up to the positive output of the supply voltage through the resistor (in Fig. 4 not shown), connected to the base of the transistor 21, the emitter of which is connected to the "common" power terminal, and the collector is connected to the first terminal of the energy pumping winding 7, the second terminal of which is connected to the positive terminal 22 nutrition.

Measuring amplifier 13 is known from the book. Kofman R., Driskol F. Operational Amplifiers and Linear Integrated Circuits. - M .: Mir, 1979, p. 148 and can be performed on standard operational amplifiers such as KP544UD2. The comparator 14 can be performed on the KP554CA3, and the trigger 17, the OR element 16 and the transistor 21, respectively, on the K555TM2, K555LE1 and KT3102.

As a shaper of 15 time intervals, a multi-channel programmable pulse generator can be used (see the description of the invention to the USSR patent JV ° 1757085, class H 03 K 3/64. Multi-channel programmable pulse generator). Moreover, all the connections of the generator 11 and the clock inputs of the timers 14 (see the drawing for the description of the patent N »1757085) are broken. One of the three timers 14-1 include in the frequency divider mode. Its synchronization input is used in a device that implements the method as a synchroinput of the shaper 15 time intervals, and the output included in the group of 33-1 outputs is connected to the synchroin of one of the timers 14-2 included in the standby mode

SUBSTITUTE SHEET (RULE 26) multivibrator, the output of the waiting multivibrator included in the group of outputs 33-2, is used as the output of the shaper 15 time intervals.

A detailed description of the operation of the timers 14-1, 14-2, .... 14-N and the operating parameters in the modes of the frequency divider and the standby multivibrator are described in book. edited by Shakhnov B.A.

Directory. Microprocessors and microprocessor sets of integrated circuits. T. 1. - M .: Radio and communications, 1988, p. 76-82.

The I2-24 instrument described in the book was selected as a time interval meter. edited by V.A. Kuznetsov Directory. Measurements in electronics. - M .: Energoatomizdat, 1987, p. 351.

The computer 19 may be of the type IBM PC.

The first 23 and second 24 conclusions of the energy pumping coil 7, as well as the first 25 and second 26 conclusions of the information reading coil 8 are made of platinum, soldered into the cover 5 (see Fig. 1) and connected respectively (see Fig. 4) to the collector transistor 21, with a positive output 22 of the power supply and with the inputs of the measuring amplifier 13.

We will consider the operation of the device using an example of an absolute pressure sensor that can be directly placed in a measured medium, for example, silicone oil or an inert filling (halocarbon).

The device operates as follows.

After turning on the power, the computer program 19 sets, in accordance with the description of the invention to the USSR patent JV2 1757085, the operating modes of the timers 14-1, 14-2 (not shown in Fig. 4) of the shaper 15 time intervals. Channel 0 of timer 14-1 (on FIG. 4 is not shown) set to mode 2 - frequency divider. Channel 0 of the timer 14-2 (not shown in Fig. 4) is set to mode 1 of the standby multivibrator. In this case, the outputs of these channels are set to a single state. Thus, at the information input of the trigger 17 set the level of the logical unit. The inputs of the sample timers 14-1 and 14-2 (not shown in Fig. 4) are supplied with logic zero levels that prohibit the operation of timers. The meter 18 time intervals through the public channel using a computer 19 is set to measure the pulse duration.

Then, a single pulse is supplied to the start input 20 and then to the second input of the OR element 16, for example, from a parallel channel (not shown in Fig. 4), the computer 19, or by means of the button and time delay. A positive pulse arrives at the base of transistor 21, which opens transistor 21, and a current begins to flow through the energy pumping winding 7, which induces an EMF, an electromotive force of induction in an oscillatory circuit in which electromagnetic oscillations occur.

When the pressure of the measured medium P (see Fig. 1) changes, the membrane 1 and the flat conductive spiral of the inductor 2 deform, the overlap area and the distance between the flat conductive spiral of the inductor 2 and the conductive coating 9 change.

As a result, the intrinsic capacitance of the inductor 2 is changed, which is the capacitance distributed along the winding of the inductor 2 by changing the capacitive coupling, the capacitance between the individual sections of the winding of the inductor 2, the inductance of the inductor 2, the capacitance and frequency of the oscillation circuit.

SUBSTITUTE SHEET (RULE 26) The frequency of the resonant oscillations of the oscillatory circuit is measured by taking information from the coil 8 of the read information. The conclusions of the read coil 8 are connected to the direct inputs of the measuring amplifier 13, which amplifies the signal. Then the signal from the output of the measuring amplifier 13 is fed to the direct input of the comparator 14, to the inverse input of which a reference voltage is supplied. From the output of the comparator 14, positive rectangular signals are fed to the first input of the OR element 16 (a logic zero level is supplied to the second input of the OR element 16 at that time), the sync input of the driver 15 time intervals and to the sync input of the trigger 17. From the output of the OR 16 element, rectangular pulses arrive to the base of the transistor 21, upon opening of which a current flows through the energy pumping coil 7, upon changing which an induction emf arises in the oscillating circuit, under the action of which currents appear in the oscillating circuit, according to Asynchronous with the direction of the current in the inductor 2 in each half-cycle of the oscillation of the oscillatory circuit. Moreover, in the positive half-period of oscillations in the oscillating circuit, energy is pumped during an increase in current in the energy pumping coil 7, and in the negative half-period of oscillations, energy is pumping during a decrease in current in the energy-pumping coil 7, since energy transfer occurs at the moment of change in current in the coil 7 paging energy. Thus, continuous undamped resonant vibrations with energy pumping at certain instants of time are excited in the oscillatory circuit, increase the amplitude of oscillations at these moments, convert these oscillations into digital form, and determine the oscillation frequency of the oscillatory circuit.

SUBSTITUTE SHEET (RULE 26) Next, the computer program 19 feeds from the start block (not shown in FIG. 4) to the enable inputs of the timers 14-1, 14-2 (not shown in FIG. 4) the logical unit levels and allows their operation. In this case, one of the timers of group 14-1 (not shown in Fig. 4), set to the frequency divider mode, begins to divide the input frequency coming from the output of the comparator 14 to the sync input of the shaper 15 time intervals by the number n set using the computer program into the counter of channel 0 of the timer (not shown in FIG. 4). At the output of this timer (not shown in Fig. 4), at the end of the count, a negative pulse is generated each time, the duration of which is equal to the length of the frequency period of the input signal coming from the output of the comparator 14. From the output of the frequency divider (not shown in Fig. 4), the signal arrives to the synchronization input of the timer of the group of timers 14-2 (not shown in Fig. 4) of the time interval shaper 15, which operates in the multivibrator standby mode, and starts the multivibrator in standby mode due to the negative input pulse difference (in Fig. 4 shown), whose output is set to logic zero. This logical zero is fed to the information input of the trigger 17, which is set to the zero state on the positive edge of the pulse coming from the output of the comparator 14 and forms the beginning of the time interval, which starts measuring 18 time intervals. The waiting multivibrator (not shown in Fig. 4) of the shaper 15 time intervals decrements the number recorded in its counter (counts the number of negative pulses arriving at its sync input from the output of the divider (not shown in Fig. 4) frequencies) and, upon receipt of a given number of pulses, set exit to the level of a logical unit. Wherein

SUBSTITUTE SHEET (RULE 26) on the first positive edge of the pulse coming from the output of the comparator 14 to the sync input of the trigger 17, the trigger 17 is set to a single state and forms the closure of the measurement of the time interval for the meter 18 time interval. The trigger 17 is necessary in order to eliminate the influence of the time delays of switching along the edges when the counters (in Fig. 4 not shown) of the shaper 15 time intervals are triggered. Formed by the trigger 17 and measured by the meter 18 time intervals, the time interval is read through the public channel using computer programs 19 and the magnitude of the frequency of oscillations in the oscillatory circuit is determined by measuring the time interval in which a given number of periods of oscillation of the oscillatory circuit fits.

Then, using the computer program 19, the pressure value of the measured medium is determined, for which the functional relationship between the oscillation frequency of the oscillating circuit and the pressure of the measured medium is determined by a preliminary calibration, the results of which are stored in the memory of the computer 19.

INDUSTRIAL APPLICABILITY The proposed pressure sensor can be made of available elements and materials in the conditions of electronic production. It will be widely used in devices of the application of the present invention, other private automation of pressure measurement will be obvious to specialists. From the description and practical forms of its implementation. This description and examples are considered as material illustrating the invention, the essence of which and the scope of patent claims are defined in the following claims, a combination of essential features and their equivalents.

SUBSTITUTE SHEET (RULE 26)

Claims

Claim

1. A pressure sensor comprising a membrane with an inductive element made in the form of a flat conductive coil of an inductor and a measuring and recording unit, characterized in that it is provided with a cover of dielectric material in the form of a disk mounted on a membrane of dielectric material, an energy pumping coil, a coil for reading information from the measuring and recording unit and a conductive coating, while the width of the first and last turns of a flat conductive coil of the coil is inductively ti is greater than the width of the middle part of turns of the inductor.

2. The sensor according to claim 1, characterized in that the lid and membrane are preferably made of fused silica.

3. The sensor according to claim 1, characterized in that the conductive coating is made in the form of a metal strip located circumferentially on the inner surface of the lid above a flat electrically conductive coil of the inductor placed on the inner side of the membrane.

4. The sensor according to claim 1, characterized in that the energy pumping coil, the information reading coil of the measuring and recording unit are made in the form of flat conductive spirals and are placed on the inner surface of the lid.

SUBSTITUTE SHEET (RULE 26)